Food poision - and How to Prevent It

Changing lifestyles in the modern world have resulted in an increased demand for ready-to-eat foods, fast foods and dining out. This change in demand has, in turn, brought with it new and increased problems. One of these is the risk of bacterial food poisoning.

This pamphlet briefy explains what food poisoning is, why it occurs, and the steps that should be taken by people involved in food preparation and service to prevent it.

  • How Does Food Poisoning Occur?

    Usually, it takes large numbers of food poisoning bacteria to be present in food in order to cause illness. However, given the right conditions, bacteria can multiply very rapidly. These conditions include:

    • Time - In ideal conditions, one bacterium can multiply to 2,097,152 within seven hours.
    • Temperature - Food poisoning bacteria grow best in the temperature range 5 degrees C - 60 degrees C.
      (See side diagram.) This is called the temperature danger zone.
    • Nutrients - Bacteria need their own food source to grow and multiply. The types of foods which bacteria prefer include dairy products, egg products, meat and poultry, smallgoods (not including salami), processed meat and chicken products, fish, shellfish and fish products.
      Because bacteria multiply rapidly in these foods, they are known as high risk foods. High risk foods which have been contaminated with food poisoning bacteria and then left in the temperature danger zone can cause food poisoning to anyone who consumes them.
    • Water - Without moisture, the growth of bacteria slows down and may stop. Drying is an effective form of food preserving.

  • How Does Food Become Contaminated?

    Food is contaminated through poor handling and storage and through lack of personal hygiene by the people who prepare and serve it. Food poisoning bacteria is very widespread. It can be found in the soil, on animals and on people. Because of this, it is possible for foods such as raw meat, poultry and vegetables to contain these bacteria from the start.

    A common way that food can become contaminated, is through cross contamination. This can occur in two ways:

    • During food preparation, hands, utensils and equipment such as cutting boards can become contaminated with bacteria from raw food. If these utensils, equipment and hands are then used to prepare ready-to-eat or cooked food, without first being thoroughly washed, then this food can become contaminated with bacteria from the raw food. As this food is not cooked again before being consumed, the bacteria in it will not be killed by cooking.
    • During storage, bacteria from raw food can contaminate ready-to-eat or cooked food if the later are not stored separately. If they are stored in the same refrigerator, raw food should always be stored in the lowest part of the refrigerator and ready-to-eat or cooked food on the shelves above. This prevents liquids from the raw food dripping on to the cooked food. Store food in clean non-toxic washable containers or cover with foil or plastic film.

  • How Can Food Poisoning Be Prevented?

    Food poisoning can be prevented by:

    (1) Preventing food from becoming contaminated.
    (2) Preventing the bacteria in the food growing and multiplying.

    We can think of food poisoning as being a chain of circumstances:

    • There must be bacteria on the food.
    • The bacteria have the right conditions to grow warmth (between 5 degrees C and 60 degrees C), moisture and food.
    • The bacteria have time to grow and multiply.

    If this chain of events can be broken, food poisoning can be prevented.

    Some of the ways of breaking this chain are:

    • Making sure your hands are clean before handling food.
    • Thoroughly washing all equipment used for preparing raw foods.
    • Storing raw foods below cooked foods in the refrigerator.
    • Making sure food is served as soon as possible after preparation.

    Some Common Food Poisoning Bacteria

    1. Salmonella
      • Commonly found in: meat, poultry, eggs and egg products.
      • Symptoms: nausea, stomach cramps, diarrhoea, fever and headache.
      • Onset: 6-72 hours after consuming contaminated food. Symptoms can last from 3 - 5 days.
    2. Bacillus
      • Commonly found in: Cereals, rice, meat products, packet soups.
      • Symptoms: nausea, stomach cramps, diarrhoea, fever and headache.
      • Onset: 1-6 hours after consuming the contaminated food. Symptoms usually last no longer than 24 hours.
      • Note: These bacteria produces spores which are not killed during cooking. When cooked food containing these spores, has been left in the temperature danger zone, the spores produce toxins (poisons) in the food which can cause food poisoning.
    3. Staphylococcus aureus
      • Commonly found in: Meat and poultry dishes, egg products, mayonnaise-based salads, cream or custard filled desserts.
      • Symptoms: acute vomiting, nausea, occasionally diarrhoea and cramps.
      • Onset: 30 minutes-8 hours after consuming the contaminated food. Symptoms usually last about 24 hours.
      • Note: These bacteria produce toxins in food. The toxin is not destroyed during cooking so correct storage of food before and after cooking is essential. These bacteria is commonly found on the skin and in the nose and mouths of healthy people.

    Therefore, it is important that you maintain high standards of personal hygiene when working with food. People with open cuts or wounds on their hands and arms must ensure that the injury is completely protected by a waterproof bandage.

    Other common food poisoning bacteria include:

    • Clostridium perfringens.
    • Vibrio parahaemolyticus.
    • Listeria monocytogenes.

    *Important: If you think you may have food poisoning, report it to your doctor. It is important that you also report it to your local council health department as soon as possible. Retain any left over food which you believe may have caused you to become ill.